Patients meeting DSM-III-R criteria for elective mutism and/or social phobia are evaluated using standardized rating scales. Adult patients with social phobia may elect to participate in a study investigating cholecystokinin systems in the neurobiology of social phobia. Adult patients with social phobia may elect to participate in a treatment study investigating the efficacy of phenelzine versus imipramine, whereas children with elective mutism are offered the opportunity to participate in a double-blind, placebo-controlled study investigating the therapeutic value of fluoxetine. Preliminary results of these studies indicate that: 1) elective mutism may be a childhood variant of social phobia; 2) children with elective mutism have positive responses to fluoxetine therapy, although a notable degree of improvement is also associated with placebo treatment in some children; 3) elective mutism and social phobia can result in significant work, school or social disability; 4) pentagastrin-induced anxiety is a useful tool in the investigation of social phobia.